I have an 87 NA with 107K miles that I use as a daily driver and have observed over the course of the last year that my oil pressure on average (dash gauge) has been slowly getting lower. Based on what I have learned here I have been running Pennzoil Platinum 5w30 with Pureone filters for the last 15K with changes every 5K. It idles hot at what I would consider the low end of spec and just a hair shy of 40 psi hot turning 3k on the freeway. Normal traffic it seems to run around 20-35 psi. No signs of knock or extra valve noise.
In previous posts jdub has mentioned that the 7M was designed to run oil with 10-12 cst viscosity at operating temp. Is going with a higher cst rating acceptable given the larger clearances of worn bearings to maintain pressure? I was looking at using Amsoil 5w40 which has 13.6 cst at ops temp which from what I can tell is on the low side compared to the rest of the field.
In previous posts jdub has mentioned that the 7M was designed to run oil with 10-12 cst viscosity at operating temp. Is going with a higher cst rating acceptable given the larger clearances of worn bearings to maintain pressure? I was looking at using Amsoil 5w40 which has 13.6 cst at ops temp which from what I can tell is on the low side compared to the rest of the field.
